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i Glossary of Transformer Terms CE: Mark to indicate third-party cUL: Mark to indicate UL Certification approved or self-certification to to specific CSA Standards. Air cooled: A transformer that is specific requirements of the European community. Decibel (dB): Unit of measure used to cooled by the natural circulation of airii around, or through, the core and coils. express the magnitude of a change in Celsius (centigrade): Metric signal or sound level. Ambient noise level: The existing temperature measure. Delta connection: A standard three-1 or inherent sound level of the area F = (1.8 x C) + 32 phase connection with the ends of surrounding the transformer, prior to each phase winding connected in energizing the transformer. Measured C = (F-32) / 1.8 series to form a closed loop with each2 in decibels. Center tap: A reduced capacity tap phase 120 degrees from the other. Ambient temperature: The temperature at the mid-point of a winding. The Sometimes referred to as three-wire. of the air surrounding the transformer3 into which the heat of the transformer center tap on three-phase delta-delta Dielectric tests: Tests that consist of transformers is called a lighting tap. the application of a voltage higher is dissipated. It provides 5% of the transformers kVA than the rated voltage for a specified4 Ampacity: The current-carrying for single-phase loads. time for the purpose of determining capacity of an electrical conductor Certified tests: Actual values taken the adequacy against breakdowns of under stated thermal conditions. during production tests and certified insulating materials and spacings5 Expressed in amperes. as applying to a given unit shipped under normal conditions. on a specific order. Certified tests are DOE 2016 efficient: A revision to Ampere: The practical unit serial numberspecific.6 of electric current. federal law 10 CFR Part 431 (2007) Common mode: Electrical noise that mandates higher efficiency for Attenuation: A decrease in signal distribution transformers manufactured or voltage fluctuation that occurs power or voltage. Unit of measure7 is dB. between all of the line leads and the for sale in the U.S. and U.S. Territories common ground, or between ground effective January 1, 2016. TP-1 Autotransformer: A transformer in and line or neutral. efficient transformers can no longer8 which part of the winding is common legally be manufactured for use in the Compensated transformer: U.S. as of this date. to both the primary and the secondary A transformer with a turns ratio circuits. Dry-type transformer: A transformer9 that provides a higher than nameplate in which the core and coils are in a gas- Banked: Two or more single-phase output (secondary) voltage at no load, transformers wired together to supply and nameplate output (secondary) eous or dry compound insulating medium. A transformer that is cooled10 a three-phase load. Three single-phase voltage at rated load. It is common by a medium other than a liquid, transformers can be banked for small transformers (2 kVA and less) together to support a three-phase load. to be compensated. normally by the circulation of air.11 For example, three 10 kVA single-phase Conductor losses: Losses (expressed E3: Eatons version of a CSL3 transformers banked together will transformer. in watts) in a transformer that are have a 30 kVA three-phase capacity. incidental to carrying a load: coil12 BIL: Basic impulse level. The ability resistance, stray loss due to stray Eddy currents: The currents that are induced in the body of a conducting of a transformers insulation system fluxes in the windings, core clamps, mass by the time variation of magnetic to withstand high voltage surges. and the like, as well as circulating13 All Eaton 600 V-class transformers currents (if any) in parallel windings. flux or varying magnetic field. have a 10 kV BIL rating. Also called load losses. Efficiency: The ratio of the power output from a transformer to the14 BTU: British thermal unit. In North Continuous duty rating: The load that total power input. Typically expressed America, the term BTU is used a transformer can handle indefinitely as a %. to describe the heat value (energy without exceeding its specified15 content) of fuels, and also to describe temperature rise. Electrostatic shield: Copper or other the power of heating and cooling conducting sheet placed between Core losses: Losses (expressed in primary and secondary windings, systems, such as furnaces, stoves,16 barbecue grills and air conditioners. watts) caused by magnetization of and grounded to reduce electrical the core and its resistance to magnetic interference and to provide additional When used as a unit of power, BTU flux. Also called no-load losses or protection from line-to-line or line-to- per hour (BTU/h) is understood,17 though this is often abbreviated to excitation losses. Core losses are ground noise. Commonly referred to always present when the transformer as Faraday shield. just BTU. is energized.18 Buck-Boost: The name of a CSA: Canadian Standards Encapsulated transformer: standard, single-phase, two-winding A transformer with its coils either Association. The Canadian equivalent dipped or cast in an epoxy resin or transformer application with the of Underwriters Laboratories (UL).19 low-voltage secondary windings other encapsulating substance. connected as an autotransformer CSL3: Candidate Standard Level 3 for boosting (increasing) or bucking (CSL3) design criteria developed by20 (decreasing) voltages in small the U.S. Department of Energy. amounts. Applications can either be single-phase or three-phase.21

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Enclosure: A surrounding case Frequency: On AC circuits, designates Hottest-spot temperature: The high-or housing used to protect the the number of times that polarity est temperature inside the transformer icontained equipment against external alternates from positive to negative winding. Is greater than the measuredconditions and prevent personnel and back again per second, such as average temperature of the coilfrom accidentally contacting live parts. 60 cycles per second. Typically conductors, when using the ii measured in Hertz (Hz). resistance change method.Environmentally preferable product:A product that has a lesser or reduced Ground: Connecting one side of Hysteresis: The tendency of a 1negative effect on human health and a circuit to the earth through low magnetic substance to persist inthe environment when compared to resistance or low impedance paths any state of magnetization.competing products that serve the to help prevent transmitting electrical Impedance: The retarding forces 2same purpose. This comparison may shock to personnel.consider raw materials acquisition, of current in an AC circuit; the Harmonic: A sinusoidal waveform with current-limiting characteristicsproduction, manufacturing, packaging, a frequency that is an integral multiple of a transformer. Symbol = Z 3distribution, reuse, operation,maintenance and disposal of the of the fundamental frequency (60 Hz). Inductance: In electrical circuits, theproduct. This term includes recyclable 60 H3 fundamental opposition to a change in the flow of 4products, recycled products and 120 H3 2nd harmonic electrical current. Symbol = Lreusable products. 180 H3 3rd harmonicEPACT: The Energy Policy Act of 1992 240 H3 4th harmonic Inducted potential test: A standard 5 dielectric test of transformer(EPAct) is an important piece of Harmonic distortion: Nonlinear insulation. Verifies the integrity oflegislation for efficiency because itestablished minimum efficiency levels distortion of a system characterized insulating materials and electrical 6 by the appearance of harmonic clearances.for dry-type distribution transformers (non-sinusoidal) currents in themanufactured or imported after Inrush current: The initial high peakDecember 2006. EPAct, which was output, when the input is sinusoidal. of current that occurs in the first few 7based on NEMA standards, defined Harmonic distortion, total (THD): The cycles of energization, which can bea number of terms, including what square root of the sum of the squares 30 to 40 times the rated current.constitutes an energy-efficient of all harmonic currents present in 8 a load, excluding the fundamental Insulating transformer: Another termtransformer. The DOE issued a rule 60 Hz current. Usually expressed as for an isolating transformer.that defines these transformers and 9how manufacturers must comply. In a percent of the fundamental. Insulation: Material with a highApril 2013, the DOE mandated even electrical resistance. High-voltage windings: In a two-higher minimum efficiency levels for 10 winding transformer, the winding Insulation materials: Those materialsdistribution transformers effective intended to have the greater used to insulate the transformersstarting in January 2016. DOE EPAct voltage. Usually marked with electrical windings from each otherrule (PDF): Energy Efficiency Program 11 H designations. and ground.for Certain Commercial and IndustrialEquipment: Test Procedures, Labeling, HMT: Harmonic Mitigating Integral TVSS or SPD: Major standardand the Certification Requirementsfor Electric Motors. Final Rule. 10-CFR Transformer (HMT) is better able to change for surge protective devices 12 handle the harmonic currents present (formerly known as transient voltagePart 431. in todays electrical power system. surge suppressors). The primaryExcitation current: No load current. The thereby increasing system capacity, safety standard for transient voltage 13 reducing distortion throughout a surge suppressors (TVSS) has under-current that flows in any winding used facility, help to minimize downtime gone major revisions in the pastto excite the transformer when all otherwindings are open-circuited. It is usually and mysterious maintenance on three years with mandatory compli- 14 equipment, and return the longevity ance by manufacturers required byexpressed in percent of the rated current of equipment life through reduced September 29, 2009. Even the name ofof a winding in which it is measured.Also called magnetizing current. operational energy losses, thereby the standard has changed from UL 15 running cooler. Standard for Safety for TransientFCAN: Full Capacity Above Nominal Voltage Surge Suppressors, UL 1449 Hp: Horsepower. The energy requiredtaps. Designates the transformer will to raise 33,000 pounds a distance of to UL Standard for Safety for Surge 16deliver its rated kVA when connected Protective Devices, UL 1449. This one foot in one minute. 1 hp is equalto a voltage source which is higher means that TVSS listed to the UL 1449 to 746 watts, or 0.746 kW. 17than the rated primary voltage. 2nd Edition standard will no longer Hi pot: A standard test on dry-type be able to be manufactured afterFCBN: Full Capacity Below Nominal transformers consisting of extra-high September 29, 2009. All Surgetaps. Designates the transformer will potentials (voltages) connected to the Protective Devices must be designed, 18deliver its rated kVA when connected windings. Used to check the integrity tested, manufactured and listed toto a voltage source which is lower than of insulation materials and clearances. the UL 1449 3rd Edition standard afterthe rated primary voltage. this date. 19

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Isolating transformer: A transformer Non-ventilated transformer: Reactor: A single winding device withi where the input (primary) windings A transformer where the core and an air or iron core that produces a are not connected to the output coil assembly is mounted inside specific amount of inductive reactance (secondary) windings (i.e., electrically an enclosure with no openings for into a circuit. Normally used to reduceii isolated). ventilation. Also referred to as totally of control current. enclosed non-ventilated (TENV). K-factor: A common industry term for Regulation: Usually expressed as1 the amount of harmonics produced by No load losses: Losses in a the percent change in output voltage a given load. The larger the K-factor, transformer that is excited at rated when the load goes from full load to the more harmonics that are present. voltage and frequency but that is no load.2 Also used to define a transformers abil- not supplying a load. No load losses Scott T connection: Connection for ity to withstand the additional heating include core losses, dielectric losses generated by harmonic currents. and conductor losses in the winding three-phase transformers. Instead of using three sets of coils for a three-3 kVA: Kilovolt-ampere. Designates due to the exciting current. Also phase load, the transformer uses only referred to as excitation losses. the output that a transformer can two sets of coils. deliver for a specified time at a Overload capability: Short-term4 rated secondary voltage and rated overload capacity is designed into Series/multiple winding: A winding frequency without exceeding the transformers as required by ANSI. consisting of two or more sections that specified temperature rise. When Continuous overload capacity is can be connected for series operation5 multiplied by the power factor, will not deliberately designed into a or multiple (parallel) operation. Also give kilowatts or kW. transformer because the design called series-parallel winding. objective is to be within the allowed6 1000 VA = 1 kVA winding temperature rise with Short circuit: A low resistance connection, usually accidental, Lamination: Thin sheets of electrical nameplate loading. across part of a circuit, resulting in7 steel used to construct the core of Percent IR (% resistance): Voltage drop excessive current flow. a transformer. due to resistance at rated current in Sound levels: All transformers make Limiting temperature: The maximum percent of rated voltage. some sound mainly due to the8 temperature at which a component vibration generated in its core by Percent IX (% reactance): Voltage drop or material may be operated due to reactance at rated current in alternating flux. All Eaton general- continuously with no sacrifice purpose dry-type distribution9 in normal life expectancy. percent of rated voltage. transformers are designed with Percent IZ (% impedance): Voltage sound levels lower than NEMA ST-20 Linear load: A load where the current drop due to impedance at rated maximum levels.10 waveform conforms to that of the current in percent of rated voltage. applied voltage, or a load where Star connection: Same as a wye a change in current is directly Phase: Type of AC electrical circuit; connection.11 proportional to a change in usually single-phase two- or three-wire, applied voltage. or three-phase three- or four-wire. Step-down transformer: A trans- former where the input voltage is12 Live part: Any component consisting Polarity test: A standard test greater than the output voltage. of an electrically conductive material on transformers to determine that can be energized under conditions instantaneous direction of the Step-up transformer: A transformer where the input voltage is less than the13 of normal use. voltages in the primary compared output voltage. to the secondary. Load losses: I2R losses in windings. Also see conductor losses. Primary taps: Taps added to the T-T connection: See Scott T connection.14 primary (input) winding. See Tap. Low-voltage winding: In a two- Tap: A connection brought out of winding transformer, the winding Primary voltage: The input circuit a winding at some point between15 intended to have the lesser voltage. voltage. its extremities, usually to permit Usually marked with X designations. changing the voltage or current ratio. Power factor: The cosine of the phase Taps are typically used to compensate16 Mid-tap: See center tap. angle between a voltage and a current. for above or below rated input voltage, in order to provide the rated output Noise level: The relative intensity of Ratio test: A standard test of voltage. See FCAN and FCBN. sound, measured in decibels (dB). transformers to determine the ratio17 NEMA Standard ST-20 outlines the of the input (primary) voltage to the Temperature class: The maximum tem- maximum allowable noise level for output (secondary) voltage. perature that the insulation system of dry-type transformers. a transformer can continuously with-18 Reactance: The effect of inductive stand. The common insulation classes Nonlinear load: A load where the and capacitive components of a are 105, 150, 180 (also 185) and 220. current waveform does not conform to circuit producing other than unity19 that of the applied voltage, or where a power factor. Temperature rise: The increase over change in current is not proportional to ambient temperature of the windings a change in applied voltage. due to energizing and loading the20 transformer.

3 10 CFR Part 431 Energy-Efficient Ventilated Transformer Harmonic Mitigating Ventilated Transformer Ventilated Transformer Eaton K-Factor nonlinear transformersEatons family of energy-efficient are specifically designed to withstand Eatons harmonic mitigating trans- 4ventilated transformers meet DOE the harmful overheating effects caused formers (HMTs) are specially designed2016 efficiency requirements and by harmonics generated by nonlinear transformers that treat a wide varietyfederal energy efficiency laws man- (non-sinusoidal) loads. These loads of harmonics. Also called phase- 5dated by the Energy Policy Act of include computers, laser printers, shifting transformers, their low zero-2005 and 10 CFR Part 431 (2016). copiers and other office equipment, sequence impedance wye zig-zagDistribution transformers installed in as well as video monitors and other secondary windings prevent harmful 6the United States are required to meet electronic equipment. The core and triplen (3rd, 9th, 15th, etc.) harmonicthese energy efficiency requirements. coils of K-Factor transformers are currents from coupling into the primary 7Energy-efficient transformers are especially designed to have reduced delta, where they can progressespecially designed to have low no induction levels, which result in a upstream to the service entrance.load (core) losses. Minimum efficiency reduction in stray losses. Oversized Multiple HMTs with a variety of phase- 8levels have been established for these (200% rated) neutrals and electrostatic shift configurations can be applied intransformers when loaded at 35% of shielding are provided as standard on a coordinated scheme to target 5th,their full load capacity. Available 600 V. K-Factor transformers. Eaton K-Factor 7th, and higher order harmonics at 9Eaton offers a wide variety of energy- transformers are available in ratings the common bus feeding all of theefficient transformers, including with a K-factor of 4, 9, 13, 20, 30, 40 transformers. HMTs are ideally suited150 C, 115 C or 80 C; general and 50. 600 V-class single-phase for installations rich in harmonic loads, 10purpose or K-factor rated; with models are available to 167 kVA; such as educational facilities (K-12aluminum or copper windings. three-phase ratings to 1500 kVA. and universities), government,Eatons energy-efficient transformers Eatons family of K-Factor transformers commercial, medical and call-center applications. HMTs are manufactured 11are manufactured with a NEMA 2 are manufactured with the same high-enclosure as standard, and are suit- quality construction features as our with the same high-quality featuresable for installation outdoors when ventilated transformer products, as Eatons ventilated transformers, 12a NEMA 3R weathershield kit is including NEMA 2 enclosures and the including NEMA 2 enclosures and theinstalled. Eatons energy-efficient 220 C (Class R) insulation system with 220 C (Class R) insulation system withtransformers use a 220 C insulation 150 C temperature rise as standard. 150 C temperature rise as standard. 13system with 150 C temperature rise Additionally, Eatons HMTs areas standard. Refer to Page 19.1-10 for additional manufactured with a 200% neutral information. Eaton K-FactorratedInstallation of energy-efficient transformers are available to meet all and electrostatic shield as standard. 14transformers may help facilities 10 CFR Part 431 efficiency levels, Refer to Page 19.1-11 for additionalearn points toward LEED certification including DOE 2016 efficiency. information.from the U.S. Green Building Council. 15 HMTs are available in four configurations: 16 Type NON (0 phase-shift) Type THR (30) Type POS (+15) 17 Type NEG (15)

Available in three-phase ratings to 18

1000 kVA and 600 V. Eaton HMTs are available to meet all 10 CFR Part 431 efficiency levels, including 19 DOE 2016 efficiency.

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i Motor Drive Isolation Hazardous Location MiniPower Center

Transformers Transformersii

3 Motor Drive Isolation Ventilated Transformer4 Eatons motor drive isolation trans- Hazardous Location Transformers MiniPower Center formers are especially designed for An Eaton minipower center replaces Eatons hazardous location transformers three-phase, SCR-controlled, variable-5 speed motor drive load profiles. Sized are suitable for use in environments three individual components: classified by the National Electrical Primary main breaker by horsepower and common motor Code (NEC) as Class I, Division 2, voltages, motor drive isolation trans- Transformer6 formers are braced to withstand the Groups A, B, C and D, as defined by NEC Article 501, when installed in Distribution loadcenter. mechanical stresses associated with compliance with NEC-recommended AC adjustable frequency drives or The minipower center combines7 DC drives. Available in three-phase procedures for dry-type transformers all three into a single unit. All inter- rated 600 V and below. As defined by ventilated designs to 1500 hp and connecting wiring is performed at the NEC Article 500, Class I, Division 2 600 V. Epoxy encapsulated three- factory. Minipower centers are ideally8 phase designs are available to 20 hp. locations include atmospheres that suited for applications where 120 V may contain volatile or ignitable Motor drive isolation transformers are is required at a remote location. concentrations of flammable liquids manufactured using the same high- Parking lots, workbenches and9 quality construction features as our or gas vapors, or locations adjacent to temporary power on construction such environments. Acetone, ammonia, ventilated transformer products, sites are common applications for benzene, gasoline, methane, propane including NEMA 2 enclosures and the minipower centers. Available in10 220 C (Class R) insulation system with and natural gas are examples of single-phase and three-phase ratings such substances. 150 C temperature rise as standard. to 600 V, 100 A, and 30 kVA with Epoxy encapsulated models have secondary loadcenters with11 NEMA 3R enclosures and 115 C Eatons hazardous location transformers provisions for up to 24 single-pole are of the encapsulated design, and are temperature rise as standard. All Eaton available up to 600 V ratings. Single- branch breakers. Available with12 three-phase ventilated motor drive phase ratings 0.05 kVA through 25 kVA; aluminum bus and plug-on branch isolation transformers include a three-phase ratings to 112.5 kVA. breakers, or with copper bus and normally open dry contact temperature Aluminum windings are standard, bolt-on branch breakers.13 sensor installed in the coils; encapsu- with copper as an option. Hazardous lated models are not available with Minipower centers incorporate an location transformers use a 180 C this sensor. This sensor can be encapsulated transformer in their insulation system with 115 C connected to provide advance alert construction, and are NEMA 3R14 or warning of a potential overheating temperature rise as standard. rated for outdoor applications. Eatons 80 C rise is an available option. of the transformer. minipower centers are UL Listed for Refer to Page 19.1-16 for additional use as service entrance devices.15 Refer to Page 19.1-15 for additional information. information. Refer to Page 19.1-17 for additional information.16 Read the text on Page 19.0-5 on the Energy Policy Act of 2005 before specifying these units. These units are17 exempt from 10 CFR Part 431 efficiency requirements.

are typically installed where sensitive Type Approved by the American Buck-Boost Transformersloads such as input circuits of Bureau of Shipping (ABS) for on-board Eatons Buck-Boost transformers arecomputers, medical equipment and use in steel vessels (not for propulsion ideally suited to applications where 5microprocessors require additional systems or combat vessels). These the available voltage needs to beprotection from high-frequency transformers are typically installed slightly increased (boosted) orelectrical disturbances. Shielded below deck in electrical or mechanical decreased (bucked) to be used in 6isolation transformers include an rooms where the ambient temperature a specific application. When Buck-electrostatic shield (Faraday shield) is greater than normal. Eatons marine- Boost transformers are wired asinstalled between the primary andsecondary windings. This shield is duty transformers are especially designed for operation in 50 C autotransformers, they can be used 7 to accomplish this bucking or boostinggrounded to the core of the transformer ambient locations. Marine-duty rated of voltage. Buck-Boost transformersto attenuate high-frequency electrical transformers are manufactured are single-phase encapsulated 8disturbances in the load from being with copper windings as standard. transformers and are available intransmitted to the line side of the Encapsulated designs are available in three voltage combinations;transformer. Shielded isolation single-phase ratings 0.05 kVA through 120 x 24012/24 9transformers are available in all 37.5 kVA; three-phase designs 15 kVAsizes and ratings of encapsulated and through 112.5 kVA. Ventilated designs 120 x 24016/32ventilated transformers. By design, are available in single-phase ratings of 240 x 48024/48 10all K Factor and harmonic mitigating 15 kVA through 250 kVA; three-phasetransformers include a single, designs 15 kVA through 1000 kVA. ...and are available in 0.05 kVA throughaluminum electrostatic shield Encapsulated and ventilated models 7.5 kVA. These transformers can also 11as standard. are available up to 600 V ratings. The be used at their nameplate voltages standard temperature rise of Eatons for applications such as low-voltageShielded isolation transformers areavailable that meet 10 CFR Part 431 marine-duty transformers is 115 C. interior or landscape lighting. 12(DOE 2016) efficiency requirements. Read the text on Page 19.0-5 on the Energy Policy Act of 2005 beforeRead the text on Page 19.0-5 on specifying these units. 13the Energy Policy Act of 2005 beforespecifying these units. 14

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i General Construction Insulation System Core and Coil Assemblies

Features of General Purpose Industry standards classify insulation The transformer core is constructed systems and temperature rise as using high-grade, non-aging, siliconii (DOE 2016, including shown below. steel with high magnetic permeability, K-Factor DOE 2016 and Table 19.1-1. Insulation System Classified and low hysteresis and eddy current losses. Maximum magnetic flux HMT DOE 2016) Ventilated1 Ambient + Winding + Hot = Temp. densities are substantially below Transformers Rated 600 V Temperature Rise Spot Class the saturation point. The transformer core volume allows for efficient and below 40 C 80 C 30 C 150 C2 40 C 115 C 30 C 185 C transformer operation at 10% above 40 C 150 C 30 C 220 C the nominal tap voltage. The core General Description laminations are tightly clamped and3 Eatons single-phase and three-phase The design life of transformers having different insulation systems is the compressed. Coils are wound of general purpose dry-type ventilated electrical grade aluminum or copper, transformers are of the two-winding same; the lower temperature systems and are of continuous wound4 type, self-cooled, and are available in a are designed for the same life as the construction. The BIL (basic impulse wide variety of primary and secondary higher temperature systems. level) for all 600 V-class windings is voltage combinations. 10 kV. The core and coil assembly Most Eaton ventilated transformers,5 Eatons transformers are designed, regardless of their temperature rise, is installed on neoprene vibration- absorbing pads. manufactured and tested in accordance are manufactured using a 220 C with all of the latest applicable ANSI, insulation system. Required Ventilated transformers with wye-6 NEMA and IEEE standards. All 600 V performance is obtained without connected secondaries have the class ventilated transformers with exceeding the insulation system neutral brought out to a separate ratings through 1500 kVA are UL rating at rated temperature rise in XO terminal or busbar.7 listed and bear the UL label. Open a 40 C maximum ambient, with an average ambient temperature The core and coil assembly is core and coil assemblies are UR of 30 C over a 24-hour period. grounded to the transformer enclosure8 labeled products. Transformers manufactured with by means of a visible flexible copper These transformers are designed for 220C insulation system meet the ground strap. The copper ground continuous operation at rated kVA for requirements of NEC 450.21(b) strap is sized per the NEC to be a9 24 hours a day, 365 days a year, with Exception No.2. It is not necessary grounding conductor. normal life expectancy as defined in to install them in a special, fire- Eaton three-phase DOE 2016 efficient ANSI C57.96. resistant room.10 transformers are provided with a Efficiency validation: Eaton- All insulation materials used are bonding ground bar attached to the manufactured transformers in flame-retardant and do not support bottom panel for compliance with11 compliance with 10 CFR Part 431 combustion as defined in ASTM NEC 450.10(A). (2016), DOE 2016 efficient bear the Standard Test Method D635. UL Energy Efficiency Verification Mark Electrostatic Shielding12 to confirm that the transformer meets There are no industry standards the energy efficiency requirements set for electrostatic shield performance. forth in federal law 10 CFR Part 431. Eaton-manufactured transformers13 have been tested by an independent laboratory to meet the following attenuation levels:14 When tested per MIL-Std-220A, Method of Insertion Loss Measurement, with15 matched impedance no load technique: 1. Common mode noise attenuation:16 Minus 80 dBA minimum at 0.1 kHz to 1.5 kHz; minus 55 dBA minimum at 1.51 kHz to 100 kHz.17 2. Normal mode (Transverse mode) noise attenuation: Minus 35 dBA minimum at 1.5 kHz to 10 kHz.18 Primary to Secondary Capacitance of 24.7418.06 picofarads on the range19 10020 kHz.

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Taps All ventilation openings are protected All Eaton ventilated transformers arePrimary taps are available on most against falling dirt. Proper installation designed to have audible sound levels i of weathershields on ventilated lower than those required by NEMAEaton ventilated transformers to transformers makes the enclosure ST-20 (2014). However, considerationallow compensation for source NEMA 3R rated and suitable for should be given to the specific location iivoltage variations. outdoor use. of a transformer and its installation to minimize the potential for soundWinding Terminations To ensure proper ventilation and transmission to surrounding structures 1Primary and secondary windings are cooling of the transformer, follow and sound reflection. Installationterminated in the wiring compartment. manufacturers recommended clear- and ambient conditions at a specificEncapsulated units have copper leads ances around ventilation openings. location can result in field-measured 2or stabs brought out for connections. Installation Clearances audible sound levels as much asVentilated transformers have leads 15 dBA greater than those levelsbrought out to aluminum or copper Eatons transformers should be installed with a minimum clearance around the measured in a sound-proof chamber. 3pads that are pre-drilled to accept The following installation methods transformer enclosure to preventCu/Al lugs. Aluminum-wound trans- should be considered:formers have aluminum pads; copper- accidental contact with flammable or 4 combustible materials. The minimum 1. If possible, mount the transformerwound transformers have copper required clearance from the back panel away from corners of walls orpads. Lugs are not supplied with Eatontransformers; however, lug kits are varies by transformer design. Many ceilings. For installations that 5 small kVA ventilated transformers must be near a corner, useavailable as a field-installed accessory. (150 kVA and smaller) require just 2 sound-absorbing materials onEaton recommends external cables berated 90 C (sized at 75 C ampacity) inches of clearance, while larger kVA the walls and ceiling if necessary 6 transformers require 6-inch clearance to eliminate reflection.for encapsulated designs and rated or more. Minimum installation clear-75 C for ventilated designs. 2. Provide a solid foundation for ances are stated on the nameplate of mounting the transformer and 7 all transformers. The NEC requires aSeries-Multiple Windings minimum of 36 inches clearance in front use vibration dampening mountsSeries-multiple windings consist of of the transformer for safe installation if not already provided in the 8two similar coils in each winding that and maintenance. Care should be taken transformer. Eatons ventilatedcan be connected in series or parallel to avoid restricting the airflow through transformers contain a built-in(multiple). Transformers with series- the bottom of the transformer. vibration dampening system 9multiple windings are designated with to minimize and isolate soundan x or a / between the voltage Transformers should be located in transmission. However, areas not accessible to the public. supplemental vibrationratings, such as voltages of 240 x 480 dampening mounts installed 10or 120/240. If the series-multiplewinding is designated by an x, Sound Levels between the floor and thethe winding can be connected only All transformers emit some audible transformer may provide 11in series or parallel. With a / sound due mainly to the vibration additional sound dampening.designation, a mid-point also becomes generated in their core by alternatingavailable in addition to the series or flux. NEMA ST-20 defines the 12parallel connection. As an example, a maximum average sound levels240 x 480 winding can be connected for transformers.for either 240 (parallel) or 480 (series). 13A 120/240 winding can be connected Table 19.1-2. NEMA ST-20 (2014) Maximum Audible Sound Levels for 600 V Class Transformers (dBA)for either 120 (parallel) or 240 (series),or 240 with a 120 mid-point. Equivalent Winding kVA Average Sound Level, Decibels 14 Self-Cooled Ventilated Self-Cooled Sealed RangeEnclosures A B C DThe transformer enclosure is made of K Factor = 1 K Factor = 13 Forced Air When 15 K Factor = 4 K Factor = 20 Fans Runningheavy-gauge steel and is finished using K Factor = 9a continuous process of degreasing,cleaning and phosphatizing, followed 3.00 and below 40 40 67 45 16by electrostatic deposition of a thermo- 3.01 to 9.00 40 40 67 45setting polyester powder coating and 9.01 to 15.00 45 45 67 50subsequent baking. The coating color 15.01 to 30.00 45 45 67 50 17is ANSI 61 and is UL recognized for 30.01 to 50.00 45 48 67 50 50.01 to 75.00 50 53 67 55outdoor use. In compliance withNEMA ST-20, Eatons ventilated 75.01 to 112.50 50 53 67 55 18 112.51 to 150.00 50 53 67 55transformers are designed such that 150.01 to 225.00 55 58 67 57the maximum temperature on the topof the enclosure does not exceed 50 C 225.01 to 300.00 55 58 67 57 19 300.01 to 500.00 60 63 67 59rise above the ambient temperature. 500.01 to 700.00 62 65 67 61For ventilated transformers, the 700.01 to 1000.00 64 67 67 63 20 Greater than 1000 Consult factoryenclosure construction is ventilated,drip-proof, NEMA 2, with lifting Note: Consult factory for nonlinear requirements exceeding a K-factor rating of 20.provisions. When the fans are not running, columns A and B apply. Sound levels are measured using 21 the A-weighted scale (dBA).

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iFeatures of General Purpose The transformer core is constructed Series-multiple windings consist using high-grade, non-aging, silicon of two similar coils in each windingEncapsulated Transformers steel with high-magnetic permeability, that can be connected in series or iiRated 600 V and Below and low hysteresis and eddy current parallel (multiple). Transformers with losses. Maximum magnetic flux series-multiple windings are desig-General Description densities are substantially below nated with an x or a / between the 1 the saturation point. The transformer voltage ratings, such as voltages ofEatons single-phase and three-phase core volume allows for efficient 240 x 480 or 120/240. If the series-general purpose encapsulated dry-typetransformers are of the two-winding transformer operation at 10% above multiple winding is designated by 2 the nominal tap voltage. The core an x, the winding can be connectedtype, self-cooled, and are available in a laminations are tightly clamped only in series or parallel. With a /wide variety of primary and secondaryvoltage combinations. and compressed. Coils are wound designation, a mid-point also becomes 3 of electrical grade aluminum or available in addition to the series orEatons transformers are designed, copper, and are of continuous wound parallel connection. As an example, amanufactured and tested in accordance construction. The BIL (basic impulse 240 x 480 winding can be connected 4with all of the latest applicable ANSI, level) for all 600 V-class windings for either 240 (parallel) or 480 (series).NEMA and IEEE standards. All 600 V- is 10 kV. In encapsulated transformers, A 120/240 winding can be connectedclass encapsulated transformers with the core and coil assembly is for either 120 (parallel) or 240 (series), 5ratings through 112.5 kVA are UL listed completely encased in a proportioned or 240 with a 120 mid-point.and CSA certified, and bear the UL and mixture of resin or epoxy, andCSA labels. aggregate to provide a moisture- Enclosures 6 proof, shock-resistant seal. The core The transformer enclosure is made ofThese transformers are designed for and coil encapsulation system is heavy-gauge steel and is finished usingcontinuous operation at rated kVA designed to minimize the audible a continuous process of degreasing, 7for 24 hours a day, 365 days a year, sound level. cleaning and phosphatizing, followedwith normal life expectancy as by electrostatic deposition of a thermo-defined in ANSI C57.96. Encapsulated Taps setting polyester powder coating and 8transformers are outside the scope Primary taps are available on many subsequent baking. The coating colorof U.S. energy efficiency law 10 CFR Eaton encapsulated transformers is ANSI 61 and is UL recognized forPart 431 (DOE 2016). to allow compensation for source outdoor use. In compliance with 9 voltage variations. NEMA ST-20, Eatons transformersInsulation Systems are designed such that the maximumIndustry standards classify insulation Winding Terminations temperature on the top of the enclosure 10systems and temperature rise as Primary and secondary windings are does not exceed 50 C rise above theshown below. ambient temperature. terminated in the wiring compartment. 11Table 19.1-5. Insulation System Classification Encapsulated units have copper leads For encapsulated transformers, the or stabs brought out for connections. standard enclosure construction is Ambient + + = Temperature Winding Hot Temp. Ventilated transformers have leads totally enclosed, non-ventilated 12 Rise Spot Class brought out to aluminum or copper NEMA 3R, with lifting provisions. pads that are pre-drilled to accept NEMA 4X rated encapsulated 40 C 40 C 55 C 80 C 10 C 30 C 105 C 150 C Cu/Al lugs. Aluminum-wound trans- transformers are available as 13 25 C 135 C 20 C 180 C formers have aluminum pads; copper- an option. 40 C 115 C 30 C 185 C wound transformers have copper 40 C 150 C 30 C 220 C pads. Lugs are not supplied with Wall mounting brackets are 14 Eatons transformers; however, lug provided on many Eaton encapsulatedThe design life of transformers having kits are available as a field-installed transformers. These mountingdifferent insulation systems is the accessory. Eaton recommends brackets are designed to provide the 15same; the lower temperature systems external cables be rated 90 C (sized proper spacing between the mountingare designed for the same life as at 75 C ampacity) for encapsulated surface and the transformer enclosure.the higher temperature systems. designs and rated 75 C for ventilated To ensure proper ventilation and 16 designs.Eatons encapsulated transformers cooling of the transformer, followare manufactured using a 180 C manufacturers recommendedinsulation system. Required clearances around encapsulated 17performance is obtained without transformers.exceeding the insulation system rating 18at rated temperature rise in a 40 Cmaximum ambient, with an averageambient temperature of 30 C over a 1924-hour period.All insulation materials are flame-retardant and do not support 20combustion as defined in ASTMStandard Test Method D635. 21

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Sound Levels Table 19.1-6. NEMA ST-20 (2014) Maximum Audible Sound Levels for 600 V Class Transformers (dBA)i All transformers emit some audible Equivalent Average Sound Level, Decibels Winding kVA Self-Cooled Ventilated Self-Cooled Sealed sound due mainly to the vibration Rangeii generated in their core by alternating flux. NEMA ST-20 defines the A B C D K Factor = 1 K Factor = 13 Forced Air When maximum average sound levels K Factor = 4 K Factor = 20 Fans Running K Factor = 91 for transformers. All Eaton encapsulated transformers 3.00 and below 40 40 67 45 3.01 to 9.00 40 40 67 45 are designed to have audible sound2 levels lower than those required by 9.01 to 15.00 45 45 67 50 15.01 to 30.00 45 45 67 50 NEMA ST-20 (2014). However, 30.01 to 50.00 45 48 67 50 consideration should be given to3 the specific location of a transformer 50.01 to 75.00 50 53 67 55 75.01 to 112.50 50 53 67 55 and its installation to minimize the 112.51 to 150.00 50 53 67 55 potential for sound transmission to4 surrounding structures and sound 150.01 to 225.00 55 58 67 57 225.01 to 300.00 55 58 67 57 reflection. Installation and ambient 300.01 to 500.00 60 63 67 59 conditions at a specific location can 500.01 to 700.00 62 65 67 615 result in field-measured audible sound 700.01 to 1000.00 64 67 67 63 levels as much as 15 dBA greater than Greater than 1000 Consult factory those levels measured in a sound-proof6 chamber. The following installation Note: Consult factory for nonlinear requirements exceeding a K-factor rating of 20. When the fans are not running, columns A and B apply. Sound levels are measured using methods should be considered: the A-weighted scale (dBA).7 1. If possible, mount the transformer away from corners of walls or ceilings. For installations that must8 be near a corner, use sound- absorbing materials on the walls and ceiling if necessary9 to eliminate reflection. 2. Provide a solid foundation for10 mounting the transformer and use vibration-dampening mounts if not already provided in the11 transformer. Eatons encapsulated transformers use a special encapsulation system to minimize12 and isolate sound transmission. However, supplemental vibration dampening mounts installed13 between the floor and the transformer may provide for additional sound dampening.14 3. Make electrical connections to the transformer using flexible conduit.15 4. Locate the transformer in an area where audible sound is not offensive to building inhabitants.16 5. If a transformer is going to be installed in a location where17 the audible sound could be objectionable, consider installing a transformer specifically designed18 to have reduced sound levels. Eaton offers many transformers with a sound reduction up to 5 dB19 below NEMA ST-20 limits.

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K-Factor Rated Nonlinear Installation Clearances K = (Ih)2(h)2

i Eatons ventilated transformers should Transformers Rated 600 V be installed with minimum clearances Ih = Percent Current at Harmonic h and Below as noted on the transformers name- h = Harmonic Order, i.e., 3rd, 5th, 7thii plate. Most Eaton transformers require Applications a minimum of 6 inches clearance For example, a load that is 90% of the behind the transformer; however, many fundamental, 30% of the third harmonic,1 Eaton K-Factor transformers are specifically designed to withstand the small kVA ventilated transformers may and 20% of the fifth harmonic would be installed with just 2 inches clearance, yield (.9)2(1)2 + (.3)2(3)2 + (.2)2(5)2 or harmful overheating effects caused by a K-factor of 2.62. This load would harmonics generated by nonlinear while large kVA transformers require2 (non-sinusoidal) loads. These loads 12 inches or more of clearance behind require a transformer with a K-factor the transformer. Minimum installation rating of 4. include computers, laser printers, copiers and other office equipment, clearances are stated on the nameplate3 as well as video monitors and other of all transformers. The NEC requires Transformers that carry a K-factor rating define the transformers ability to electronic equipment. Eaton K-Factor a minimum of 36 inches clearance in withstand a given harmonic load while transformers are not simply over-sized front of the transformer. Care should be4 transformers. The core and coils of taken to avoid restricting the airflow operating within the transformers insulation class. our K-Factor transformers are specially through the bottom of the transformer. designed to have reduced induction Transformers should be located in areas An analysis of harmonic loads and5 levels, which results in a reduction in not accessible to the public. a calculation of the K-factor must be stray losses. Oversized (200% rated) made to properly apply transformers neutrals and electrostatic shielding Wiring Compartment in any building or facility. Note that6 are typical features found in our Eatons ventilated transformers have the calculated K-factor is not constant K-Factor transformers. Eaton K-Factor wiring compartments sized to comply since nonlinear loads change transformers are manufactured with with NEMA and NEC standards. throughout the day as equipment7 the same high-quality construction and lighting is turned off and on. features as our other ventilated The K-factor These harmonic loads also change transformer products, including A common industry term for the over the life of the building or facility8 NEMA 2 enclosures as standard. amount of harmonics produced by a as equipment is added or removed. given load is the K-factor. The larger Technical Data the K-factor, the more harmonics are Harmonic Currents9 present. Linear loads, for example, Harmonic currents are found in nonlinear Available Ratings have a K-factor of 1. Transformers may loads. These currents are generated by Eaton K-Factor transformers are carry a K-factor rating to define the various types of equipment including10 available in a wide range of ratings transformers ability to withstand switching mode power supplies that to meet specific voltage conversion the additional heating generated abruptly switch current on and off during requirements. Eaton offers transformers by harmonic currents. each line cycle. Switching mode power11 with K-factor ratings of 4, 9, 13, 20, 30, supplies or diode capacitor power 40 and 50. Calculating the K-factor supplies convert AC line voltage to low- All nonlinear waveforms can be voltage DC. This process accomplished12 kVA Capacity broken down mathematically into by charging capacitors during each line Single-phase ventilated designs are a fundamental frequency and its cycle with narrow pulses of current that available in ratings from 15 kVA harmonics. IEEE C57.110 establishes are time-coincident with line voltage13 through 250 kVA; three-phase ratings a direct relationship between these peaks. Examples of this equipment 15 kVA through 1500 kVA. harmonics and transformer heating. include electronic ballasts for fluorescent Underwriters Laboratories has lighting, personal computers, printers,14 Insulation System and Temperature Rise established a similar relationship, the fax machines, electronic and medical Eaton-manufactured ventilated K-factor, which is derived by summing test equipment uninterruptible power transformers are manufactured the square of the percentage current at supplies and solid-state motor drives.15 using a 220 C insulation system with a given harmonic level multiplied by 150 C temperature rise as standard. the square of the harmonic order. Note: Nonlinear is synonymous with the Low temperature rise designs term non-sinusoidal.16 (115 C and 80 C temperature rise) are available as options.

17 Frequency Most ventilated transformers are designed to operate in 60 Hz systems.18 50/60 Hz designs are available as an option. Eatons ventilated transformers can be designed to operate at a variety19 of frequencies. Winding Material20 Aluminum conductor and terminations are provided as standard on ventilated transformers. Copper winding conduc-21 tors and terminations are available as Figure 19.1-1. Harmonic Currents Found in Nonlinear Loads Cause Wave Shape Distortion and an option. Create Added Stresses on Transformers

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Harmonic Mitigating kVA Capacity Application Considerations

i Three-phase ratings 15 kVA through Eaton offers harmonic mitigatingTransformers Rated 600 V 1000 kVA. transformers with four differentand Below Insulation System and Temperature Rise phase-shift options: ii Eatons harmonic mitigating trans- Type NON (0 phase-shift)Applications formers are manufactured using a Type POS (+15 phase-shift)Eatons harmonic mitigating trans- 220 C insulation system with 150 C Type NEG (15 phase-shift) 1formers (HMTs) are specially designed temperature rise as standard. Lowtransformers that treat a wide variety Type THR (30 phase-shift) temperature rise designs (115 C andof harmonics. Also called phase- 80 C temperature rise) are available To select the proper HMT, the 2shifting transformers, their low zero- as options. nonlinear load profile of a particularsequence impedance wye zig-zag application must be known.secondary windings prevent harmful Frequency 3triplen (3rd, 9th, 15th, etc.) harmonic Eatons harmonic mitigating trans- Type NON (0) HMTs are ideallycurrents from coupling into the pri- formers are designed to operate in suited for treating 3rd and other triplenmary delta, where they can progress 60 Hz systems. 50/60 Hz designs are harmonics that are the signature of 4upstream to the service entrance. available as an option. The transformers single-phase nonlinear loads. This isMultiple HMTs with a variety of phase- can be designed to operate at a variety the most common application encoun-shift configurations can be applied in of frequencies. tered. Type NON HMTs use electro- 5a coordinated scheme to target 5th, 7th magnetic flux cancellation to canceland higher-order harmonics at the Winding Material triplen harmonics. There, harmonicscommon bus feeding all of the trans- Copper conductor and terminations are treated in the secondary windings 6formers. HMTs are ideally suited for are provided as standard on harmonic and prevented from coupling into theinstallations rich in harmonic loads, mitigating transformers. Aluminum primary delta windings, where theysuch as educational facilities (K12 and winding conductors and terminations may be transmitted upstream to the 7universities), government, commercial, are available as an option. service entrance location. Type NONmedical and call-center applications. HMTs can be deployed singly to treatHMTs are manufactured with the Installation Clearances triplen harmonics. As with most other 8same high-quality features as Eatons Eatons ventilated transformers should harmonic mitigating methods, theventilated transformers, including be installed with minimum clearances closer the HMT can be installed toNEMA 2 enclosures and the 220 C as noted on the transformers name- the load, the greater the benefit. 9(Class R) insulation system with plate. Most Eaton transformers require150 C temperature rise as standard. a minimum of 6 inches clearance Type POS (+15) and Type NEG (15)Additionally, Eatons HMTs are behind the transformer; however, harmonic mitigating transformers are 10manufactured with a 200% neutral many small kVA ventilated transformers typically used together in coordinatedand electrostatic shield as standard. may be installed with just 2 inches pairs to treat 5th, 7th and otherEatons harmonic mitigating venti- clearance, while large kVA transformers harmonics that are generated by three- 11lated transformers are designed pri- require 12 inches or more of clearance phase nonlinear loads. 5th, 7th andmarily for indoor installations. behind the transformer. Minimum higher order harmonics pass throughVentilated transformers have NEMA 2 installation clearances are stated on the harmonic mitigating transformers, 12enclosures as standard, and are suit- the nameplate of all transformers. The to a point of common coupling; theable for installation outdoors when NEC requires a minimum of 36 inches first common electrical point that isNEMA 3R weathershield kits are clearance in front of the transformer. shared by the HMTs. At this common 13installed. Ventilated transformers are Care should be taken to avoid restricting point, balanced portions of the 5th,typically floor-mounted on an elevated the airflow through the bottom of the 7th, etc., harmonic currents arehousekeeping pad. When properly transformer. Transformers should be canceled and prevented from flowing 14supported, they are also suitable for located in areas not accessible to further upstream in the distributionwall mounting or trapeze-mounting the public. system. Type POS and Type NEGfrom ceilings. HMTs have nearly identical electrical 15 Wiring Compartment characteristics, including zero-Technical Data Eatons ventilated transformers have sequence and positive-sequence wiring compartments sized to comply impedance and reactance. The more 16Available Ratings with NEMA and NEC standards. closely matched the coordinated pairs of transformers, the more thoroughEatons harmonic mitigating trans-formers are available in a wide range Thermal Sensors the harmonic cancellation. 17of ratings to meet specific voltage Harmonic mitigating transformers are Coordinated pairs of Type NON andconversion requirements. Eatons available with warning and/or alarm Type THR transformers, as well asHMTs accept a three-phase three-wire thermal sensors imbedded in their coils. coordinated pairs of Type NON, Type 18input and have a three-phase four-wire Thermal sensors are normally open dry THR, Type POS and Type NEG HMTs(phases and neutral) output. contacts that can be wired to provide provide treatment of 3rd and other a signal to remote locations to indicate triplen harmonics within their 19 a potential heating problem within the secondary windings. This cancellation transformer coils. Contacts are rated 180 C (warning) and 200 C (alarm). is achieved by virtue of their wye zig-zag winding configuration. 20

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i Harmonic Mitigating Transformers What are Harmonics?

An understanding of how harmonics As our world becomes even more the electrical distribution system. are generated and what harmonics dependent on electrical and electronic The difficult thing about harmonic really are is necessary in order toii equipment, there is an increased distortion is determining the source. understand how HMTs can provide likelihood that operations will Once this task has been completed, harmonic mitigation. Electronic equip- experience the negative effects of the solution can be easy. Harmonic ment requires DC voltage to operate.1 harmonic distortion. The productivity mitigating transformers (HMTs) are Rectifiers and capacitors are used to and efficiency gains achieved from one of the many possible solutions convert AC voltage to DC voltage increasingly sophisticated pieces to help eliminate these harmful within the equipment. These devices2 of equipment have a drawback: harmonics. are frequently referred to as switch increased harmonic distortion in mode power supplies. As the capaci- tors charge and discharge during this3 conversion, the capacitor draws cur- rent in pulses, not at a continuous rate. This irregular current demand, as4 depicted in Figure 19.1-2, distorts the linear 60 Hz sine wave. As a result, these types of loads are commonly referred5 to as non-sinusoidal, or nonlinear. As shown in Figures 19.1-3 and 19.1-4,6 the waveform created by the nonlinear source is actually the mathematical sum of several sine waves, each with 60 Hz7 fundamental a different frequency and magnitude. Each of these individual waveforms is called a harmonic, and is identified by8 its frequency relative to the fundamental frequency, 60 Hz. In other words, each individual harmonic is identified by a Figure 19.1-2. Typical Waveform of Single-Phase Devices9 number, which is the number of com- plete cycles the specific harmonic goes through in a single 60 Hz cycle.10 In Figure 19.1-4, the fundamental frequency is 60 Hz. The fundamental frequency is assigned the harmonic11 number of 1, and is the benchmark for all other harmonic numbering. The fundamental, 60 Hz sine wave completes12 60 full cycles in one second. The 3rd harmonic completes three full cycles in the time it takes the fundamental to13 complete just one cycle, or 180 cycles per second. Likewise, the 5th harmonic completes five full cycles in the time14 it takes the fundamental harmonic to Figure 19.1-3. Composite Waveform complete a single cycle, which equates to 300 cycles per second. Odd multiples15 of the 3rd harmonic (3rd, 9th,15th, 21st, etc.) are commonly referred to as triplen harmonics.16 The proliferation of electronic equipment (including computers, fax machines, copiers, electronic ballasts, office17 equipment, cash registers, slot machines, 7th electronic monitoring devices, video 5th games, medical diagnostic equipment18 3rd fundamental and the like) is what makes single-phase devices the most common source of harmonics. These devices generate a typ-19 ical waveform shown in Figure 19.1-2, and have a harmonic profile as shown in Table 19.1-9. As one can see, the pre-20 Figure 19.1-4. Components of a Nonlinear Waveform dominant harmonic is the 3rd harmonic. Three-phase, nonlinear loads such as21 drives, on the other hand, are typically rich in 5th and 7th harmonics.

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What Problems do Harmonic currents flowing upstream What do HMTs do?

Harmonics Cause? from nonlinear loads, through the HMTs are an economical solution in i system impedance of cables andThe distorted current waveform that is transformers, create harmonic voltage the battle against the harmful effects ofcreated by nonlinear loads can cause distortion. When linear loads, like harmonics. HMTs are passive devices: iimany problems in an electrical distri- motors, are subjected to harmonic they dont have any moving parts andbution system. Depending upon the voltage distortion, they will draw a they are typically energized 24 hoursseverity of the harmonic distortion, nonlinear harmonic current. As with a day, 7 days a week, 365 days a year. 1the negative effects of harmonics may distribution transformers, harmonic This means that they are always onbe tolerable, and the installation of currents cause increased heating, the job treating harmonics, regardlessa K-factorrated transformer may be due to iron and copper losses, in of the level of load they are serving 2an adequate solution. K-factorrated motors and generators. This increased at a given point in time. Whenevertransformers do not provide any heating can reduce the life of the the HMT is energized, it will provideharmonic treatment. Rather, they are motor, as well as the motors effi- harmonic treatment. 3designed to withstand the destructive ciency. In electrical cables, harmonic Harmonic mitigating transformers areeffects of the additional heat generated currents may also create increased commonly referred to as phase-shift-by harmonic currents in the heating, which can lead to premature ing transformers. The HMT offering 4transformers windings. aging of the electrical insulation. from Eatons electrical business has Nuisance tripping of the circuit break- delta-connected primary windingsIn many instances, the harmful effects ers protecting the cable may also and wye zig-zag connected secondary 5of harmonics are too severe, and occur. Communications equipmentsimply tolerating them is not an windings. The use of wye zig-zag sec- and data processing equipment are ondary windings allows a transformeracceptable option. Harmonic currents especially susceptible to the harmful to be designed in a wide variety of 6can cause excessive heating in distri- effects of harmonics because they relybution transformers. This additional different phase-shifts (30, 15, on a nearly perfect sinusoidal input. 0, +15). In standard delta-wyeheat not only reduces the life expec- This equipment may malfunction, or transformers, including K-factorrated 7tancy of a transformer, it also reduces even fail, when installed in systemsthe usable capacity of the transformer. transformers, triplen harmonics are that are rich in harmonics. passed from the secondary windingsAnother side effect is that the audible into the primary delta windings, where 8noise of a transformer may be ampli- The costs associated with downtimefied when installed in a system that resulting from the malfunction or fail- they are trapped and circulate. In HMTs, the electromagnetic fluxcontains harmonics. ure of electrical or electronic equip- cancellation created by the wye zig-zag 9 ment can be staggering. These costsAn important characteristic of can easily surpass thousands, if not winding configuration prevents 3rdharmonics is that they are transmitted millions, of dollars per hour in lost and other triplen harmonics from 10upstream from the load, to the trans- production or lost productivity. In being transmitted into the primaryformers secondary windings, through addition to the well-defined costs delta winding. Harmonic treatment isthe primary windings of the trans- associated with the most catastrophic provided entirely by electromagnetic 11former, back to the service entrance, of harmonic effects, there are many flux cancellation; no filters, capacitorsand eventually to the utility lines. less quantitative costs that are often or other such devices are used. It overlooked when evaluating the need is important to remember that the 12 for harmonic mitigation. The increased harmonic currents still flow in the heating caused by harmonics in secondary windings. cables, motors and transformers 13 increases the cooling requirements in air-conditioned areas. The same increases in heating result in increased 14 maintenance costs and more frequent equipment replacement in order to avoid failures that could shut down 15 a building for a period of time.

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i In addition to improved system presence of electronic devices creates The closer that an HMT can be located nonlinear load profiles. Nonlinear reliability and reduced maintenance loads cause the losses in distribution to the load, the greater the benefitsii costs, HMTs also have excellent energy-saving characteristics. With transformers to increase, thereby of harmonic treatment. Installation of a large capacity HMT at the service reducing their realized efficiency. the cost of electricity continuing to Therefore, 10 CFR Part 431 efficiency entrance of a large building would1 increase around the world, there is compliance may not be a true indica- certainly provide some harmonic treat- an ever-increasing interest in energy- tion of the efficiency of a transformer ment. However, installation of several efficient products. In many facilities, exposed to nonlinear loads. Though smaller rated HMTs, perhaps one2 the cost of electricity is the second a measure of linear load efficiency, or more on each floor of a building, largest expense, eclipsed only by Eatons family of HMTs meets the provides greater benefits that will be salaries and wages. efficiency standards set forth in noticed throughout the facility. For this3 Transformers consume energy 10 CFR Part 431. Because HMTs are reason, the most popular HMTs will be intended to be installed in systems rated 75 kVA and less. This comple- even when they are lightly loaded or ments the cost-efficiencies that can be not loaded at all. Significant energy that contain high levels of nonlinear4 savings may be attained if the no-load loads, Eatons family of HMTs is gained by distributing higher voltages designed to meet the 10 CFR Part 431 through smaller cables to the point losses of a transformer are reduced. where a safer, lower voltage is needed 10 CFR Part 431 addresses this issue by efficiency levels when applied to5 requiring high efficiency levels when a nonlinear load profiles with 100% to operate equipment. transformer is loaded at 35% of its full harmonic distortion, across a broad When connecting the loads to capacity. However, this standard range of load levels, not just the the transformer, it is important to6 applies to linear load profiles only, 35% load level used in 10 CFR Part 431. remember that the balanced portion and tests to validate compliance with These energy savings are realized of the harmonic loads will be treated. 10 CFR Part 431 are performed using over the entire life of the transformer. To achieve the maximum harmonic7 linear loads. treatment, when considering the Table 19.1-9. Typical Harmonic Profile of Single-Phase Switched Mode Power Supply triplen harmonics that are treated in the secondary windings, each phase8 Harmonic Magnitude should be balanced, and the harmonic 1 1.000 profile of the loads should be as similar as possible. When treating 5th,9 3 5 0.810 0.606 7th and higher order harmonics by 7 0.370 using multiple transformers, the 9 0.157 loads should likewise have similar10 11 0.024 harmonic profiles, and the kVA and 13 0.063 15 0.079 impedance of the transformers should11 be identical as well. For example, two 75 kVA HMTs can be paired with a single 150 kVA HMT to provide12 maximum harmonic performance. In instances where transformers of unequal kVA are used in combination,13 harmonic treatment is provided for the lowest kVA load. For example, if, instead of pairing two 75 kVA HMTs14 with a single 150 kVA HMT, one would pair two 45 kVA HMTs with a 150 kVA HMT. Only 90 kVA (two times 45 kVA)15 of the 150 kVA load would be treated (if they were fully loaded). In real-world situations, it is nearly16 impossible to have perfectly matched loads. However, the benefits of treating harmonics, even in situations17 where the loads are unbalanced, are a far superior option than to not treat them at all.18 Eaton HMT transformers comply with applicable 10 CFR Part 431 efficiency standards.19

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Motor Drive Isolation Technical Data Winding Material

i Aluminum conductor and terminationsTransformers Rated 600 V Available Ratings are provided as standard on ventilatedand Below Eatons motor drive isolation trans- transformers. Copper winding conduc- ii formers are available in a wide range tors and terminations are available asApplications of ratings to meet specific voltage an option. For encapsulated designs, conversion requirements. Available most models rated 2 kVA and belowEatons motor drive isolation trans- in three-phase ventilated designs to are constructed using copper wind- 1formers are especially designed for 1500 hp and 600 V; epoxy encapsu- ings; 3 kVA and larger designs havethree-phase SCR controlled, variable lated three-phase designs are available aluminum windings as standard,speed motor drives load profiles. Sized to 20 hp. with copper windings available as 2by horsepower and common motor an option.voltages, motor drive isolation trans- kVA Capacityformers are braced to withstand the Eatons motor drive isolation encapsu- Installation Clearances 3mechanical stresses associated with lated and ventilated transformers are Eatons ventilated transformers shouldAC adjustable frequency drives or DC available in the same kVA ratings as be installed with minimum clearancesdrives. Two-winding drive isolation general purpose encapsulated and as noted on the transformers name- 4transformers provide: ventilated transformers. plate. Most Eaton transformers require a minimum of 6 inches clearance Electrical isolation between the Insulation System and Temperature Rise behind the transformer; however, many 5 incoming line and the drive circuitry Eatons motor drive isolation ventilated small kVA ventilated transformers may Voltage conversion on input line to transformers are manufactured using be installed with just 2 inches clearance, standard drive input voltages a 220 C insulation system with 150 C while large kVA transformers require 6 Help to minimize line disturbances temperature rise as standard. 115 C or 12 inches or more of clearance behind caused by SCR firing 80 C temperature rise are available as the transformer. Minimum installation Reduce short-circuit currents and an option. Encapsulated designs use clearances are stated on the nameplate 7 voltage line transients a 180 C insulation system with 115 C of all transformers. The NEC requires temperature rise as standard. 80 C a minimum of 36 inches clearance inMotor drive isolation transformers temperature rise is available as an front of the transformer. Care should be 8are manufactured using the same option on encapsulated transformers. taken to avoid restricting the airflowhigh-quality construction features as through the bottom of the transformer.our ventilated transformer products, Frequency Transformers should be located in areas 9including NEMA 2 enclosures and the Most motor drive isolation transform- not accessible to the public.220 C (Class R) insulation system as ers are designed to operate in 60 Hzstandard. Epoxy encapsulated models systems. 50/60 Hz designs are available Wiring Compartment 10have NEMA 3R enclosures and 115 C as an option. Eatons transformers can Eatons motor drive isolation trans-temperature rise as standard. All Eaton be designed to operate at a variety of formers have wiring compartmentsthree-phase ventilated motor drive iso- frequencies. sized to comply with NEMA and NEC 11lation transformers include a normally standards.open dry contact temperature sensorinstalled in the coils. This sensor can Thermal Sensors 12be connected to provide advance alert Eatons motor drive isolation trans-or warning of a potential overheating formers are provided with thermalof the transformer. Ventilated trans- sensors imbedded in their coils. The 13formers are typically floor-mounted on thermal sensors have normally openan elevated housekeeping pad. When dry contacts that can be wired toproperly supported, they are also provide a signal to remote locations 14suitable for wall mounting or trapeze- to indicate a potential heating problemmounting from ceilings. Encapsulated within the transformer coils. Contactsdesigns are typically wall-mounted are rated for 180 C. 15through 15 kVA; larger designs arefloor-mount. 16Motor drive isolation transformersare outside the scope of U.S. energyefficiency federal law 10 CFR Part 431. 17However, motor drive isolationtransformers are included in thescope of energy efficiency laws in 18other countries, such as Canada.

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i Hazardous Location Technical Data Frequency

Most hazardous location transformers Transformers Rated 600 V Available Ratings are designed to operate in 60 Hzii and Below Eatons hazardous location transformers systems. 50/60 Hz designs are available are available in the same ratings as sand as an option. Eatons transformers can Applications and resin encapsulated transformers. be designed to operate at a variety Hazardous location transformers are of frequencies.1 Eatons hazardous location transform- available in a wide range of ratings to ers are suitable for use in environments meet specific customer requirements. Winding Material classified by the National Electrical Code Copper conductors and terminations2 (NEC) as Class I, Division 2, Groups A, kVA Capacity are provided as standard on Eatons B, C and D, as defined by NEC Article Single-phase designs are available hazardous location transformers rated 501, when installed in compliance with in ratings from 0.05 kVA through 2 kVA and less. Aluminum conductor3 NEC-recommended procedures for 37.5 kVA; three-phase ratings and terminations are provided as dry-type transformers rated 600 V 3112.5 kVA. standard on hazardous location and below. transformers rated 3 kVA and greater.4 As defined by NEC Article 500, Class I, Insulation System and Temperature Rise Copper winding conductors and Division 2 locations include atmospheres Eatons hazardous location transformers terminations are available as an option. are manufactured using a 180 C insu-5 that may contain volatile or ignitable lation system with 115 C temperature Installation Clearances concentrations of flammable liquids or gas vapors, or locations adjacent to rise as standard. 80 C temperature Eatons wall-mounted hazardous rise is available as an option. location transformers have a specially6 such environments. Acetone, ammonia, designed hanger bracket that spaces benzene, gasoline, methane, propane and natural gas are examples of the transformer an adequate distance from the mounting surface.7 such substances. Eatons hazardous location transform- Transformers should be located in ers are of the encapsulated design, areas not accessible to the public.8 and are available up to 600 V ratings. Single-phase ratings 0.0537.5 kVA; three-phase ratings to 112.5 kVA.9 Hazardous location transformers use a 180 C insulation system with 115 C temperature rise.10 When provided in a grade 304 or 316 stainless steel enclosure, Eatons11 hazardous location transformers meet the corrosion-resistance requirements of a NEMA 3RX enclosure rating.12 Hazardous location transformers can be mounted in any position indoors, and only in upright positions for13 outdoor installations. NEMA 4X rated enclosures manufactured using either grade 304 or 316 stainless steel are14 available as an option. Encapsulated transformers, including15 Class I Division 2 transformers, are outside the scope of 10 CFR Part 431 energy efficiency requirements.16

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MiniPower Centers Technical Data Wiring Compartments

i Eatons minipower centers have wiringRated 600 V and Below Available Ratings compartments sized to comply with Eatons minipower centers are NEMA and NEC standards. AmpleApplications available in single-phase and three- conduit knockouts are provided to offer iiAn Eaton minipower center replaces phase ratings to 600 V, 100 A and ready access. The wiring compartmentthree individual components: 30 kVA with secondary loadcenters of wall-mounted transformers is located with provisions for up to 24 single-pole in the bottom portion of the enclosure. 1 Primary main breaker branch breakers. Minipower centers Transformer are available in a wide range of ratings Primary Main Breakers Distribution loadcenter to meet specific voltage conversion Minipower centers are provided with 2 requirements. primary main circuit breakers that...by combining all three into a single have an interrupting rating of 14 kAIC.unit. All interconnecting wiring is kVA Capacity EHD primary main circuit breakers are 3performed at the factory. Minipower Single-phase designs are available provided as standard on minipowercenters are ideally suited for applica- in ratings from 3 kVA through 25 kVA; centers with a 480 V primary; 600 Vtions where 120 V is required at a three-phase ratings 15 kVA through designs have an FD primary main 4remote location. Parking lots, work- 30 kVA. breaker as standard. Primary mainbenches and temporary power on circuit breakers with greater AICconstruction sites are common Insulation System and Temperature Rise ratings are available as an option on 5applications for minipower centers. Minipower centers are manufactured minipower centers with plug-onAvailable with aluminum bus and using a 180 C insulation system with secondary circuit breakers.plug-on branch breakers, or with 115 C temperature rise as standard. 6copper bus and bolt-on branch 80 C temperature rise is available as Optional primary main breakers arebreakers. Minipower centers an option. FD (rate 25 kAIC at 480 V; 18 kAICincorporate an encapsulated at 600 V), HFD (65 kAIC at 480 V; 7transformer in their construction. Frequency 25 kAIC at 600 V) or FDC (100 kAICPrimary main breakers are available Most minipower centers are designed at 480 V; 35 kAIC at 600 V).in a variety of interrupting ratings. to operate in 60 Hz systems. 50/60 Hz 8 Branch Circuit BreakersWhen provided in a grade 316 stain- designs are available as an option.less steel enclosure, the Eaton mini Eatons minipower centers can be Eatons minipower centers arepower center meets the corrosion- designed to operate at a variety of available with a tin-plated aluminum 9resistance requirements of a NEMA frequencies. bus loadcenter interior that accepts3RX enclosure rating. Minipower 1-inch plug-on branch circuit breakerscenters should be mounted in upright Winding Material Type BR family. 10positions only for all installations. Aluminum conductor and terminations The all-copper minipower center are provided as standard on encapsu-Minipower centers are outside the lated transformers rated 3 kVA and is constructed with a copper-wound 11scope of energy efficiency mandates, transformer and tin-plated copper greater. Copper winding conductorsincluding 10 CFR Part 431. bus loadcenter interior that accepts and terminations are available as an option. Copper windings are 1-inch bolt-on branch breakers 12 Type BAB family. standard in the all-copper model. Installation Clearances 13 Eatons minipower centers are designed to be wall-mounted. They have a specially designed hanger 14 bracket that spaces the minipower center an adequate distance from the mounting surface. 15 Minipower centers should be located in areas not accessible to the public. 16

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i Frequently Asked Questions What are Insulation Classes?

Insulation classes were originally used to distinguish About Transformers insulating materials operating at different temperatures. Can 60 Hz transformers be used at other frequencies? In the past, letters were used for the different designations.ii Recently, insulation system temperatures (C) have replaced Transformers rated for 60 Hz can be applied to circuits with the letters designations. a higher frequency, as long as the nameplate voltages are1 not exceeded. The higher the frequency that you apply to a Table 19.1-30. Insulation Classes 60 Hz transformer, the less voltage regulation you will have. Previous Insulation System 60 Hz transformers may be used at lower frequencies, but Designation Rating (C)2 only at reduced voltages corresponding to the reduction in frequency. For example, a 480120 V 60 Hz transformer Class A 105 can carry rated kVA at 50 Hz but only when applied as a Class B 1503 400100 V transformer (50/60 x 480 = 400). Class F 180 Class H 220 Can single-phase transformers be used on a three-phase source? Class R 2204 Yes. Any single-phase transformer can be used on a three- phase source by connecting the primary terminals of the How do you know if the enclosure temperature is too hot? single-phase transformer to any two wires of a three-phase5 system. It does not matter whether the three-phase source is UL and CSA standards strictly regulate the highest tempera- three-phase three-wire or three-phase four-wire. The output ture that an enclosure can reach. For ventilated transformers, of the transformer will be single-phase. the temperature of the enclosure should not increase by more6 than 50 C in C ambient at full rated current. For encapsulated Can transformers be used to create three-phase power from a transformers, the temperature of the enclosure should not single-phase system? increase by more than 65 C in a 25 C ambient at full rated7 No. Single-phase transformers alone cannot be used to current. This means that it is permissible for the temperature of the enclosure to reach 90 C (194 F). Although this temper- create the phase-shifts required for a three-phase system. Phase-shifting devices (reactors or capacitors) or phase ature is very warm to the touch, it is within the allowed stan-8 converters in conjunction with transformers are required dards. A thermometer should be used to measure enclosure to change single-phase power to three-phase. temperatures, not your hand.

What considerations need to be taken into account when Can transformers be reverse-connected (reverse-fed)?9 Yes, with limitations. Eatons single-phase transformers operating transformers at high altitudes? At altitudes greater than 3300 ft (1000 m), the density of rated 3 kVA and larger can be reverse-connected without any10 the air is lesser than at lower elevations. This reduces the loss of kVA capacity or any adverse effects. Transformers ability of the air surrounding a transformer to cool it, so the rated 2 kVA and below, because there is a turns ratio temperature rise of the transformer is increased. Therefore, compensation on the low voltage winding that adjusts11 when a transformer is being installed at altitudes greater voltage between no load and full load conditions, should than 3300 ft (1000 m) above sea level, it is necessary to not be reverse-fed. derate the nameplate kVA by 0.3% for each 330 ft (100 m) Three-phase transformers with either delta-delta or delta-wye12 in excess of 3300 feet. configurations can also be reverse-connected for step-up What considerations need to be taken into account when operation. When reverse-feeding a delta-wye connected transformer, there are two important considerations to take13 operating transformers where the ambient temperature is high? into account: (1) The neutral is not connected, only the Eatons dry-type transformers are designed in accordance three-phase wires of the wye system are connected; and with ANSI standards to operate in areas where the average (2) the ground strap between X0 and the enclosure must14 maximum ambient temperature is 40 C. For operation in be removed. Due to high inrush currents that may be ambient temperatures above 40 C, there are two options: created in these applications, it is recommended that you do not reverse-feed transformers rated more than 75 kVA.15 1. Order a custom-designed transformer made for the specific application. The preferred solution is to purchase an Eaton step-up transformer designed specifically for your application. 2. Derate the nameplate kVA of a standard transformer16 by 8% for each 10 C of ambient above 40 C. Can transformers be connected in parallel? Yes, with certain restrictions. For single-phase transformers What is the normal life expectancy of a transformer? being connected in parallel, the voltages and impedances17 When a transformer is operated under ANSI/IEEE basic loading of the transformers must be equal (impedances must be conditions (ANSI C57.96), the normal life expectancy of a trans- within 7.5% of each other). For three-phase transformers, former is 20 years. The ANSI/IEEE basic loading conditions are: the same restrictions apply as for single-phase transformers,18 plus the phase shift of the transformers must be the same. A. The transformer is continuously loaded at rated kVA For example, a delta-wyeconnected transformer (30 phase and rated voltages. shift) must be connected in parallel with another delta-wye19 B. The average temperature of the ambient air during connected transformer, not a delta-deltaconnected any 24-hour period is equal to 30 C and at no time transformer (0 phase shift).

20 exceeds 40 C. C. The altitude where the transformer is installed does not exceed 3300 ft (1000 m).21

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Why is the impedance of a transformer important? How Can I Reduce Transformer Sound Levels?The impedance of a transformer is important because it is All transformers emit some audible sound due mainly to iused to determine the interrupting rating and trip rating of the vibration generated in their core by alternating flux.the circuit protection devices on the load side of the trans- NEMA ST-20 (2014) defines the maximum average soundformer. To calculate the maximum short-circuit current on levels for transformers. iithe load side of a transformer, use the following formula: Table 19.1-31. NEMA ST-20 (2014) Maximum Audible Sound Levels Maximum Short-Circuit = Full Load Current (Amps) ------------------------------------------------------------------------------- for 600 V Class Transformers (dBA) 1 Load Current (Amps) Transformer Impedance Equivalent Average Sound Level, Decibels Winding kVAFull load current for single-phase circuits is: Self-Cooled Ventilated Self- Range Cooled 2 Nameplate Volt-Amps Sealed --------------------------------------------------------------------- Load (output) Voltage A B C D K Factor = 1 K Factor = 13 Forced Air 3and for three-phase circuits the full load current is: K Factor = 4 K Factor = 20 When Fans Nameplate Volt-Amps K Factor = 9 Running ---------------------------------------------------------- 4 Load (output) Volts 3 3.00 and below 40 40 67 45 3.01 to 9.00 40 40 67 45Example: For a standard three-phase, 75 kVA transformer, 9.01 to 15.00 45 45 67 50rated 480 V delta primary and 208Y/120 V secondary (catalog 15.01 to 30.00 45 45 67 50 5number V48M28T75J) and impedance equal to 5.1%, the full 30.01 to 50.00 45 48 67 50load current is: 50.01 to 75.00 50 53 67 55 75.01 to 112.50 50 53 67 55 6 75,000 VA 112.51 to 150.00 50 53 67 55 ------------------------------- - = 208.2 A 208 V x 1.732 150.01 to 225.00 55 58 67 57 225.01 to 300.00 55 58 67 57 7The maximum short-circuit load current is: 300.01 to 500.00 60 63 67 59 500.01 to 700.00 62 65 67 61 208.2A ----------------- = 4082.4 A 0.051 700.01 to 1000.00 64 67 67 63 8 Greater than 1000 Consult factoryThe circuit breaker or fuse on the secondary side of this Note: Consult factory for nonlinear requirements exceeding atransformer would have to have a minimum interrupting K-factor rating of 20. When the fans are not running, columns A 9capacity of 4083 A at 208 V. NEMA ST-20 (1992). and B apply. Sound levels are measured using the A-weighted scale (dBA).A similar transformer with lower impedance would require 10a primary circuit breaker or fuse with a higher interrupting All Eaton transformers are designed to have audible soundcapacity. levels lower than those required by NEMA ST-20 (2014).What clearances are required around transformers when they However, consideration should be given to the specific 11 location of a transformer and its installation to minimize theare installed? potential for sound transmission to surrounding structuresAll dry-type transformers depend upon the circulation of and sound reflection. The following installation methods 12air for cooling; therefore, it is important that the flow of should be considered:air around a transformer not be impeded. Many Eatontransformers require a minimum clearance of 6 inches 1. If possible, mount the transformer away from corners 13from panels with ventilation openings. However, small of walls or ceilings. For installations that must be nearkVA DOE 2016 efficient ventilated transformers are UL a corner, use sound-absorbing materials on the wallsapproved to be installed with just 2 inches clearance, and ceiling if necessary to eliminate reflection. 14while large kVA transformers require 12 inches or moreclearance. In compliance with NEC 450.9, Eatons ventilated 2. Provide a solid foundation for mounting the transformertransformers have a note on their nameplates identifying and use vibration dampening mounts if not alreadythe minimum required clearance from the ventilation provided in the transformer. Eatons ventilated trans- 15openings and walls or other obstructions. This clearance formers contain a built-in vibration dampening systemonly addresses the ventilation needs of the transformer. to minimize and isolate sound transmission. However,There may be additional local codes and standards that supplemental vibration dampening mounts installed 16affect installation clearances. between the floor and the transformer may provide additional sound dampening.Transformers should not be mounted in such a manner that 17one unit will contribute to the additional heating of another 3. Make electrical connections to the transformer usingunit, beyond allowable temperature limits, for example, flexible conduit.where two units are mounted on a wall one above the other. 4. Locate the transformer in an area where audible sound 18 is not offensive to building inhabitants. 5. Install low sound transformers (up to 5 dB below 19 NEMA ST-20 [2014] sound limits). 20